U.S. Pat. Nos. 4,963,147; 4,962,770; and 5,089,000 incorporated herein by reference, describe a surgical instrument which is very useful in techniques for carpal tunnel release and is also useful in other surgical techniques. The instrument includes a probe in which a cutting blade and an optical system are disposed. After the probe has been inserted into a body cavity the cutting blade is extended through a lateral aperture in the probe to a position adjacent the selected tissue, while allowing the tissue manipulation to be observed.
In the surgical instrument just described the cutting blade extends through an axially fixed rotatable pivot pin. As an actuation shaft urges the cutting blade through &he pivot pin, the distal end portion of the blade sweeps through an arc to reach a fully extended position. Initially the distal tip of the blade moves toward the distal end of the probe and then moves upwardly to its fully extended position. This forward movement of the tip of the blade can be undesirable because the tip can encounter tissue which is not intended to be cut. Also, the tip of the blade is not easily visible as it is being elevated.